Typically, a radio frequency (RF) communication device includes an RF front end which, more recently, has been enabled in a RF integrated circuit. The RF front end, conventionally, has a signal source, in most cases a voltage controlled oscillator (VCO), which is ubiquitous with modern transceivers and forms an integral part of frequency synthesizers or Phase Locked Loops (PLLs). The performance of the VCO may have an effect in the overall performance of the system if not properly designed. For example, very low phase noise or very wide tuning range with low tuning sensitivity or excellent flatness for power output versus frequency change or freedom from power compression is required with low power consumption and is critical for next generation wireless applications. It is often very challenging to combine all the best performances without much tradeoff which makes the design of such VCO very difficult.
High performance VCOs generally include a tank circuit which is formed by the parallel combination of inductance and capacitance and which plays an important role in all the performance metrics. Typically wide tuning range is achieved by varying the capacitance in the tank circuit using some kind of switching element. Generally, however, the phase noise is compromised with the tuning range which in turn is compromised with power consumption.
In a synthesizer or a signal source, modern design techniques tend to lock a high frequency output signal to a low frequency reference using phase locked loops (PLLs). A frequency divider is required to form such PLLs. Conventionally, an injection locked frequency divider (ILFD) having a predetermined frequency division ratio can be designed with low power consumption and low phase noise. However, such typical ILFDs have a relative narrow operation frequency range.
Thus, what is needed is an integrated circuit architecture for RF circuits which could provide VCOs which address the performance issues of VCOs individually, while providing an improved oscillator circuit which can concurrently meet the requirements of high performance. In addition, what is needed is an ILFD which provides low power consumption and low phase noise while providing a broadened operating frequency range. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background of the disclosure.